Promotion of microtubule acetylation plays an important role in degranulation of antigen-activated mast cells.

The aim of this study was to investigate whether microtubule acetylation is triggered by antigen stimulation and how it affects mast cell degranulation. The RBL-2H3 cell line was used as a model for mast cells. Acetylation of α-tubulin was analyzed by Western blotting. Intracellular distribution of α-tubulin and acetylated α-tubulin was observed by immunostaining. Degranulation was monitored by measuring the activity of β-hexosaminidase secreted into cell supernatants. Tukey-Kramer test was used to compare differences between groups. Microtubule acetylation proceeds globally in mast cell cytoplasm after antigen stimulation in addition to accelerated formation of microtubule-organizing centers. Pretreatment with 5Z-7-oxozeaenol (5 µmol/l), an inhibitor of TGF-β-activated kinase 1, which is a key activator of α-tubulin acetyltransferase 1, did not affect the distribution and acetylation of microtubules in resting cells; however, it significantly suppressed antigen-evoked microtubule acetylation and their reorganization, and subsequent degranulation (95.0 ± 1.2% inhibition, n = 3, P < 0.01). These results provided new insight into the post-translational modifications of microtubule to regulate mast cell degranulation.